Rainfall -
Below average rainfall, one rain event

Sydney
Observatory Hill recorded 35.8 mm of rain during September, half the historical
average of 68.6 mm. The rain fell over only four rain days (average 11 days),
the fewest since 2009, all of which fell during the middle of the month.

The
only day with more than 5 mm of rain was on the 17th, when a complex low
pressure trough with embedded lows produced heavy rain across the coast. Daily
totals reached 32.2 mm at Observatory Hill, the heaviest rain day since June.
Falls were locally heavier in the eastern suburbs, some of which consequently
recorded above average rainfall for the month. The heaviest total was 88.2 mm
at Randwick Bowling Club, its wettest September day
on record.

Temperature -
Warmest September on record

September
was the warmest on record for Sydney, with a substantial number of records
broken at Observatory Hill. Mean temperatures broke records at all six major
temperature stations in the city, a consequence of widespread maximum
temperatures more than 3 °C above normal and minimum temperatures more
than 1 °C above normal, and persistent warm weather during the month.

The
average maximum temperature at Observatory Hill was 24.4 °C,
4.4 °C above the historical average for September and 1.1 °C
above the previous September record (23.3 °C in 1980), with
temperatures more typical of November weather (average 23.6 °C).

Daytime
temperatures were persistently warm during the month, with only three days
dropping below 20 °C associated with a mid-month rain event, an equal
record with September 2012 (average 17 cool days). This included 20 consecutive
days above 20 °C between August 24 and September 12, the longest such
spell on record for September and two weeks earlier than the previous record
(19 days 7-25 September 2001).

There
were also several very warm days during the month. Seven days reached at least
28 °C during the month, well above the historical average of 1 warm
day and the most on record (previous record 6 days in 1928). Three of these
days reached 30 °C, the equal-highest on record (4 other times), two of
which occurred during the first ten days of the month.

The
average minimum temperature was also the highest on record for Sydney
Observatory Hill at 13.8 °C, 2.7 °C above the historical
average. No nights dropped below 10 °C during the month for the first
time on record (average 11 nights), while 10 nights exceeded 15 °C
(average 2-3 nights), the equal highest on record with September 2009. The
warmest night was 20.1 °C on the 10th, the earliest 20 °C
night on record for Sydney.

The
warmest days also featured unusually warm mornings. The 9am temperature was
25.9 °C on the 10th, the equal-warmest on record for September and the
earliest such warm morning by two weeks (previous earliest was 24 September
2009). This record was later broken when temperatures reached 26.9 °C
at 9am on September 26, before reaching 29.9 °C at 10 am.

Other phenomena - Early season bushfires

Sydney
Airport recorded an average of 8.8 hours of bright sunshine, above the
historical average of 7.9 hours but not as sunny as September 2012 (9.2 hours).

The
prevailing wind direction was northerly, with 33% of 3 pm winds N-W and 53%
N-E, well above average for September; only 13% of 3 pm winds were southerly,
half the historical average. The northwesterly winds brought warm inland air to
Sydney, contributing to the record-breaking temperatures for the month.

There
were eight days with strong winds observed, reaching 87 km/h at the airport and
96 km/h at Kurnell on the 26th, with gusts of 91 km/h
at Port Botany on the 12th. The strong winds on the 26th caused some fallen
trees and roof damage, mostly in western Sydney.

The
combination of dry weather, warm temperatures and strong winds resulted in
significant early-season bushfire activity during the month. Major bushfires impacted western Sydney and the Blue Mountains on
the 10th, resulting in some evacuations, closed roads, and two destroyed
houses. Bushfires also burnt large areas of Barrenjoey Head in the Northern Beaches on the 28th.

Most values are the precipitation in the 24 hours to 9 am on the day indicated.
Days marked with »» are part of a longer accumulation, which is marked like this on the final day.
Values over 100 mm have been rounded to the nearest whole millimetre.
Days marked with - have a rainfall report of zero;
days left blank have no rainfall report (which often indicates no rain fell).
This table is very wide; you may have to scroll sideways to see all the days, and you may need to set the paper to 'landscape' to print.

Notes

A Monthly Climate Summary is prepared to list the main features of the weather in Sydney using the most timely and accurate information available on the date of publication; it will generally not be updated. Later information, including data that has had greater opportunity for quality control, will be presented in the Monthly Weather Review, usually published in the fourth week of the month.

This statement has been prepared based on information available at
9 am on Monday 14 October 2013.
Some checks have been made on the data, but it is possible that results will change
as new information becomes available.

Averages are long-term means based on observations from
all available years of record, which vary widely from site to site.
They are not shown for sites with less than 20 years of record, as they cannot then be calculated reliably.
The median
is sometimes more representative than the
mean
of long-term average rain.

The Rank indicates how rainfall this time compares with the climate record for the site,
based on the
decile ranking
(very low rainfall is in decile 1, low in decile 2 or 3,
average in decile 4 to 7, high in decile 8 or 9
and very high is in decile 10).
The Fraction of average shows how much rain has fallen this time as a
percentage of the long-term mean.

The ACORN-SAT dataset
is being used for temperature area averages from December 2012 onwards.
The major change from earlier datasets is that the ACORN-SAT dataset commences in 1910, rather than 1950,
and hence rankings are calculated using a larger set of years.